Apparatus for making spunbonded fabrics

ABSTRACT

A PROCESS FOR PRODUCING SPUNBONDED NONWOVENFABRICS IS DISCLOSED, WHEREIN CONTINUOUS FILAMENTS OF ORGANIC POLYMERS ARE EXTRUDED, STRETCHED TO ORIENT SAME, AND THEN ARRANGED IN FABRIC FORM ON A MOVING CONVEYOR. THE FILAMENTS ARE ARRANGED OR DISTRIBUTED ON THE MOVING CONVEYOR BY IMPACT FROM A DEFLECTOR SURFACE, WITH A FLUID JET OPERATING UPON THE POINT OF IMPACT FORM A LOCATION IN FRONT OF THE POINT OF IMPACT IN RELATION TO THE DIRECTION OF THE DEFLECTED FILAMENTS, AND IN THE SAME PLANE AS THE AXIS OF THE FILAMENTS BEFORE AND AFTER IMPACT WITH THE DEFLECTOR SURFACE. THE SUPNBONDED NONWOVEN FABRIC PRODUCED BY THE DISCLOSED PROCESS ARE MORE HOMEGENEOUS THAN PRIOR SPUNBONDED NON-WOVEN FABRICS, AND ARE SUITABLE FOR KNOWN USES OF SUCH BABRICS, SUCH AS APPAREL BACKING PADDING AND THE LIKE.

March 19, 1974 (;,MARCHAD1ER ETAL 3,798,100

AFPAHAIUS FOR MAKTNG SPUNBONDED FABRICS Filed April 26. 1972 UnitedStates Patent Int. or. 150411 3/00 U.S. Cl. 156-167 14 Claims ABSTRACTOF THE DISCLOSURE A process for producing spunbonded nonwoven fabrics isdisclosed, wherein continuous filaments of organic polymers areextruded, stretched to orient same, and then arranged in fabric form ona moving conveyor. The filaments are arranged or distributed on themoving conveyorby impact from a deflector surface, with a fluid jetoperating upon the point of impact from a location in front of the pointof impact in relation to the direction of the deflected filaments, andin the same plane as the axis of the filaments before and after impactwith the deflector surface.

The spunbonded nonwoven fabrics produced by the disclosed process aremore homogeneous than prior spunbonded non-woven fabrics, and aresuitable for known uses of such fabrics, such as apparel backing,padding and the like.

BACKGROUND OF THE INVENTION Spun-bonded non-woven textile fabrics arenon-Woven textile fabrics substantially made of continuous filamentsgenerally randomly disposed throughout the fabric.

The manufacture of spun-bonded non-woven textile fabrics generallyconsists of extruding through a draw plate a melted, or even dissolved,fiber-forming organic polymer. Depending upon the nature of theparticular polymer involved, the extruded filaments are generally nextoriented by stretching the extruded fiber bundle, generally bypneumatically stretching the filaments with one or several compressedair jets. Then, the filament bundle is deposited in a pre-determinedmanner on a moving conveyor, with the speed and the method of feedingthe conveyor being regulated to control the desired thickness and widthof the non-woven fabric, and also to increase the regularity orhomogeneous nature, thereof. After being deposited on the movingconveyor, the spun-bonded fabric is often Subjected to a calendaringstep, generally a relatively light calendaring step, preferably with theapplication of heat, to increase the cohesiveness of the final product.Generally this calendaring step causes some of the basic filaments to bebound to one another, markedly increasing the unity of the nonwovenfabric product.

As mentioned above, after the textile filaments have been extruded andstretched, the filaments are deposited on a moving receiving conveyor.The distribution of the filaments on the conveyor is normallyaccomplished with the use of deflector surfaces. The bundle of filamentsis directed upon and impinges the deflector surface at a certain angleand then, after impingement, moves in a tangential direction along andoff of the deflector surface. The deflector surfaces are in the form offlat or curved surfaces, preferably curved surfaces of revolution, whichcan be either concave or convex in relation to the direction of travelof the filaments.

It is known to utilize fixed, flat deflectors to produce relativelyregular textile fabrics, and this involves a relatively simple design.However, the width of the distributed fibers, as well as their strength,is often less than desired.

The art prefers to use deflectors which produce a greater filamentspread, as such use permits a decrease in the number of filamentextrusion or spinning positions for a given width of final fabricproduced. To achieve a sufficient filament spread, the art has useddeflectors with complex surfaces, or movable deflectors, either flat orcurved, which lead to greater filament spreads. However, these moveabledeflectors are mechanically relatively complicated, expensive, difficultto precisely regulate, and relatively untrustworthy.

U.S. Pat. 2,736,676 discloses a process for producing sheets or matsmade of strands, yarns or slivers of various materials, especially glassstrands. The glass strands are extruded, stretched, and then impinged ona deflector surface. The patent discloses that the deflector surface maybe either flat or curved, and may be fixed or moveable. The angle ofimpingement is disclosed as being between 0 and The patent discloses,with relation to FIG. 7 thereof, the use of two air jets, mounted onopposite sides of the point of impact, to laterally sweep the strandfrom the deflector surface, by alternate operation. The patent alsodiscloses, with relation to FIGS. 8 and 9 thereof, the use of an air jetoperating behind the point of impact to aid in throwing the deflectedstrand :1 further distance from the point of impact to a receivingconveyor. The process of this patent, however, still suffers the defectsof prior processes mentioned above, namely inadequate width and poorhomogeneity of the resulting product.

SUMMARY OF THE INVENTION The process of the present invention involvesthe use of a deflector surface upon which a polymeric filament isimpinged, to produce a non-woven textile fabric hav-- ing greater widthand uniformity than produced by the prior art processes. The polymer isextruded in filamentary form, and the filaments are oriented bystretching. Thereafter, the filaments are impinged on a deflectorsurface to distribute the filaments on a moving receiving conveyor. Afluid jet is associated with the deflector surface and is directed atthe point of impact of the filaments on the deflector surface. The fluidjet is located in front of the point of impact, with relation to thedirection of the deflected filaments, and the fluid jet is in the sameplane as the axis of the impinging filaments and the average axis of thedeflected filaments, and at an angle of 30- to the axis of the impingingfilaments.

DESCRIPTION OF THE INVENTION Spun-bonded non-woven textile fabrics aremanufactured by extruding filaments of a fiber-forming polymer,orienting the extruded filaments by stretching, and then distributingthe filaments on a receiving conveyor by impinging the filaments on asmooth deflector surface. The improved process of the present inventioninvolves directing a fluid jet at the point of impact of the filamentson the deflector surface from a location in front of the point ofimpact, in relation to the direction of the deflected filaments. Thefluid jet is at an angle of 30-135 to the axis of the impingingfilaments, and is in substantially the same plane as the axis of theimpinging filaments, i.e., the filaments which are about to contact thedeflector surface, and the average axis of the deflected filaments, i.e.the filaments which have contacted the deflector surface and have beendeflected towards the receiving conveyor.

Various types of filaments may be used in the present process ofmanufacturing spun-bonded non-woven textile fabrics. The filaments maybe made of fiber-forming inorganic polymers, such as glass, althoughpreferably the filaments are made of a fiber-forming organic polymer.Any of the conventional textile fiber-forming organic polymers may beused, such as cellulose acetate, nylon or other polyamide, rayon,acrylic, modacrylic and the like.

However, the present process is particularly useful in the production ofpolyester spun-bonded non-woven fabrics. Preferably, the polyester is apolyalkylene terephthalate. When the term polyalkylene terephthalate isused in the present specification, it is to be understood to apply topolymeric linear terephthalate esters formed by reacting a glycol of theseries HO (CH OH wherein n is an integer of 2 to 10, inclusive, withterephthalic acid or a lower alkyl ester of terephthalic acid, whereinthe alkyl group contains l-4 carbon atoms, such as, for example,dimethyl terephthalate. The preparation of polyalkylene terephthalatesis disclosed in U.S. Pat. No. 2,465,319 to Whinfield and Dickson, thedisclosure of which is hereby incorporated by reference. The most widelyused and commercially attractive polyalkylene terephthalate material ispolyethylene terephthalate, which is the most preferred polymer in thepractice of the process of the present invention. Polyethyleneterephthalate is generally produced by an ester interchange betweenethylene glycol and dimethyl terephthalate to form bis-2- hydroxy ethylterephthalate monomer, which is polymerized under reduced pressure andelevated temperature to polyethylene terephthalate. The fiber-formingpolymers are extruded into continuous textile filaments, generally ofabout 4 to 70 dtex.

The filaments may be extruded at extrusion rates which are conventionalin the textile field. However, it is preferred that the impinging fibersbe travelling at a speed of about 50 to 130 meters per second at thetime of impact with the deflector surface, and the extrusion rate may beaccordingly adjusted.

After extrusion, the filaments are generally stretched by an amountsufiicient to orient the polymer molecules in the filament. Generally,the stretching will be within the range of about 200 to about 400%,based on the un stretched length of the filaments. Preferably, thefilaments are stretched by pneumatic means, but other means may beutilized, such as those disclosed in the aforesaid U.S. Pat. 2,736,676,the disclosure of which is hereby incorporated by reference.

After being stretched, the filaments are directed at the deflectorsurface, and impinged on the surface, generally at the aforesaid speedof about 50 to 130 meters per second. While the angle of impingement maybe from slightly more than up to slightly less than 90, e.g. 1 to 89",it is preferred that the angle of impingement be from to 80, morepreferably to 60.

The deflector surface may be flat or curved, and if a curved surface isused, it is preferred that the curved surface be a surface ofrevolution. The curved surface may be either concave or convex, and maybe either stationary or rrnoveable, as known to the art. Any of theknown deflectors, such as those disclosed in the aforesaid U.S. Pat.2,736,676, may be used in the practice of this invention. It isimportant that the deflector present a smooth surface in order toprevent any restraint of the filaments and to prevent any filamentimpingement that might disturb the regularity of the deflectedfilaments. In normal operation, the nature of the deflector material hasno significant influence upon the formation of the spunbonded non-wovenfabric. However, it is clear that the material of which the deflectorsurface is made must have suflicient strength and resistance to abrasionso that the impingement of the filaments and the fluid jet will notdeteriorate the surface. Among suitable materials for the deflectorsurface may be mentioned soft steel, bronz, glass, ceramics, and thelike.

The fluid jet which is directed at the point of impact of the filamentswith the deflector surface is conveniently formed by passing the fluid,under pressure, through a nozzle. In the case of compressed air, the airis suitably under a pressure of between about 1 to about 4 bars. Thenozzle preferably has a circular cross-section of a diameter of 0.5 to 5millimeters, preferably 1-3 millimeters, although the nozzlecross-section can be of shapes other than circular. For instance, thenozzle may be in the form of a rectangular or eliptical slot, having itsmajor axis in the vertical plane defined by the axis of the impingingfilaments and the average axis of the deflected filaments. In any event,the nozzle cross-sectional area is preferably no larger or smaller thanthat of the circular nozzle mentioned above. It should be understoodthat the fluid pressure and nozzle areas mentioned above are notlimiting, but are decidedly preferred, as it has been observed thatlower pressures or greater cross-sectional areas produces aninsuflicient deflected filament spread, whereas higher pressures orsmaller cross-sectional areas generally adversely affect the homogeneousnature of the resultant non-woven fabric product.

Particularly good results are obtained when the fluid jet acts in amanner which does not destroy the symmetry of the impacting bundle offilaments. This is accomplished by having the fluid jet substantially inthe vertical plane which contains the axis of the impacting filamentsand the average axis of the deflected filaments. The deflected filamentswill be on diverging paths, so that some of the deflected filaments willbe in a different vertical plane than other of the deflected filaments.Therefore, an average axis must be considered. In addition, thedeflected filaments may be subjected to a sweeping action, e.g. such asthat caused by movement of the deflector surface, and this also must beconsidered when determining the average axis of the deflected filaments.The velocity of the fluid jet should not be so great as to destroy thefilament bundle symmetry.

Preferably, but not necessarily, the fluid jet is a gas, which generallyis chemically inert with respect to the filament. It is, however,possible to use a gas or other fluid which does react with thefilaments, if such action is desired. Compressed air is convenientlyused as the inert gas, as being efficient and economical, but othergases may also be used, such as nitrogen, carbon dioxide, helium and thelike, and liquids, such as Water, while not preferred, can be used aswell.

The distance from the end of the fluid jet nozzle to the point of impactof the filaments on the deflector surface will vary according to thetype of fluid, fluid pressure, nozzle size, diameter and number offilaments, and desired width of the fabric product. Generally, thenozzle will be located a few centimeters from the point of impact, butthis distance can be as great as a few decimeters. Generally, thedistance will be no greater than 5 decimeters and no less than about 2centimeters, but preferably the distance is between 2 and 5 centimeters.

Obviously, several units comprising a deflector surface and fluid jetnozzle associated therewith can be mounted side by side with each groupof filaments treated on each unit forming a portion of the final fabric.This approach permits the ready production of extremely wide spunbondednon-woven fabrics. Using this approach, care must be taken to avoid thedisturbance of one deflected group of filaments by another group at thetime of depositing the filaments on the conveyor. It is preferred todisplace the deflected group of filaments so that they contact theconveyor in a stepwise manner. This is readily done by displacing thedeflectors so that the planes of the deflected filaments leaving thedeflector surface are parallel, and the points of impact are alignedalong a straight line which is parallel to the plane of the receivingconveyor. This insures that the distance travelled by each group offilaments between the point of impact and the conveyor surface is thesame.

After the filaments are deposited on the receiving conveyor, in thegeneral form of the spun-bonded nonwoven textile fabric, the depositedfilaments are subjected to conventional treatments to improve thecohesiveness of the non-woven fabric product. Generally the use of arelatively light calendaring step is preferred, although otherapproaches, such as use of an adhesive, can also be utilized. Forpolyalkylene terephthalate filaments, a calendering step using a nippressure of 20 to 50 kilograms per centimeter and a temperature of 140to 250 C. is preferred.

The Weight of the spun-bonded non-woven fabric produced, for a givenfabric width, can be controlled by varying the speed of the receivingconveyor and/or the extrusion rate of the filaments. In the case ofpolyethylene terephthalate, the fabric weight will generally be in therange of to 500 grams per square meter, preferably 80 to 120 grams persquare meter.

The spun-bonded non-woven textile fabrics produced by the process ofthis invention are used in applications where the products of priorspun-bonded non-woven textile fabric processes are used, such as apparelbacking, padding, or the like. However, the products of the presentprocess are wider and more uniform than the products of such priorprocesses.

DESCRIPTION OF THE DRAWINGS The invention will be more readilyunderstood with reference to the accompanying drawings wherein:

FIG. 1 represents a schematic side view of the process, and

FIG. 2 illustrates a front view of the same process.

In FIGS. 1 and 2 a bundle of filaments 1, produced on an extrusiondevice (not shown) is stretched in compressed air nozzle 2. Upondischarge from the compressed air nozzle 2, the filament bundle 1impinges upon a smooth, flat, fixed deflector surface 3.

A compressed air jet 6 passing through nozzle 4 is di rected at thepoint of impact of the filament bundle 1 upon deflector surface 3. Underthe influence of both the deflector surface 3 and the compressed air jet6, the filament bundle 1 is spread regularly and travels in a tangentialdirection from the deflector surface to receiving conveyor 5, whichmoves at a speed lower than the filament speeds. The filaments aredeposited on conveyor 5 in the form of spun-bonded non-woven fabric 7.The distance between the point of impact of the filament bundle 1 on thedeflector surface 3 and the receiving conveyor 5 is regulated bydisplacement of the conveyor 5.

EXAMPLES OF THE INVENTION Example 1 Four parallel bundles of filaments,each bundle having 60 filaments of 4.4 dtex, of polyethyleneterephthalate were extruded through perforated draw plates having diesor holes 0.5 mm. in diameter, with the extrusion rate being 2.86 gramsof polymer per minute per die. The extruded filaments were thenstretched 350% of their original length by compressed air jets.

After stretching, each filament bundle was impinged on a smooth, flat,soft steel deflector plate at an impingement angle of about Compressedair under a pressure of 3 bars was passed through a nozzle having anround port of 2 mm. in diameter. The air jet, which made an angle of 90C. with the impinging filaments (that is with the filaments passingbetween the stretching device and the deflector surface) was directed atthe point of impact of the filaments upon the deflector surface and waslocated in the same plane as the axis of the impinging filaments and theaverage axis of the deflected filaments. The end of the air jet nozzlewas mm. from the point of impact. Each of the 4 deflectors anddeflecting fluid jet nozzles were displaced from each other a distanceof 28 centimeters, and arranged in a straight line.

The filaments deflected from the deflector surface were received on ahorizontal conveyor which was 400 mm. from the point of impact. A veryregular fabric having a width of 600 mm. and a weight of 200 g. persquare meter was formed by passing the fabric received on the conveyorthrough a pair of smooth steel rolls maintained at 170 C. at a nippressure of 36 kg./cm.

Repeating this example, but using no deflecting fluid jet (thecompressed air source was simply turned ofl) resulted in the productionof a more irregular spun-bonded fabric having a width of only 150 mm.

Repeating this example, but using the deflecting ap paratus disclosed inFIG. 7 of the aforesaid US. Pat. No. 2,736,676 (that is, the single airjet was transversely disposed in a perpendicular plane to the verticalplane of the axis of the impinging filaments and the average axis of thedeflected filaments) resulted in the production of a more irregularspun-bonded fabric having a width of only 150 mm., which wastransversely shifted by about 30 mm. on the receiving conveyor. Thus,the use of an air jet directed from the side of the filament bundleresulted in a displacement of the filaments on the receiving conveyor,but had no effect on the width of the resulting spunbonded fabric.

Example 2 Example 1 was repeated, except that the extruder die holeswere 0.3 mm. in diameter, producing filaments of 2.2 dtex. Thedeflecting air jet nozzle had a port in the form of a rectangular slot 4mm. long and 0.7 mm. wide, with the main axis being located in thevertical plane defined by the axis of" the impinging filaments and theaverage axis of the deflected filaments. A compressed air pressure of2.8 bars was used in the nozzle.

A highly regular fabric was obtained having a width of 650 mm.

Example 3 Polyethylene terephthalate was extruded through perforateddraw plates having die ports or holes 0.5 mm. in diameter, at anextrusion rate of 2.86 grams per minute per hole, to form a bundle of 60filaments of 4.4 dtex. The filaments were stretched 350% of theiroriginal length in a compressed air stretching nozzle. After stretching,the bundle of filaments was deflected upon a receiving apron by means ofa convex deflector surface. The convex deflector surface was formed of aportion of a revolution cone, the generators of which oriented from thebase towards the summit formed an angle of 120 with the leading axis ofthe filament bundle.

A compressed air jet was applied to the point of impact at an angle of35 with the impinging filament bundle. The air jet was formed by passingcompressed air under a pressure of 3.5 bars through a nozzle having acircular port 3 mm. in diameter, with the end of the nozzle locatedabout 30 mm. from the point of impact.

The distance from the point of impact of the filaments on the deflectorsurface to the receiving apron was about 4001 mm. and the receivingapron was inclined at a 45 ang e.

The material received on the apron was calendered at a nip pressure of30 kg./cm. and a temperature of 170 C. The resulting spun-bondednon-woven textile fabric had a width of 350 mm. and a weight of 120grams per square meter.

Repeating this example but without using a compressed air jet resultedin the production of a more irregular fabric having a width ofonly mm.

Example 4 This example involves the use of a concave deflector having acyclically oscillating motion around a vertical axis parallel to theaxis of the impinging filament bundle.

The deflector was oscillated 60 round trips per minute about its axis,with the total travel spanning 22. The deflector surface was in the formof a round half tile having a diameter of 100 mm. and a length of mm.The point of impact was at the mid-point of the tiles length. The majoraxis of the deflector made an angle of 120 with the axis of theimpinging filament bundle.

A bundle of 70 polyethylene terephthalate filaments of 8.9 dtex wereextruded through a perforated draw plate having holes 0.5 mm. indiameter at an extrusion rate of 5.2 grams of polymer per minute perhole. The extruded filaments were stretched 350% of their originallength in a compressed air stretching nozzle, and then impinged upon theabove described concave deflector. A compressed air jet was directed atthe point of impact, at an angle of 45 with the direction of theimpinging filament bundle, the air jet being located in the same planeas the axis of the impingement filament bundle and the average axis ofthe deflected filaments. The air jet was formed by passing compressedair under a pressure of 3 bars through a single nozzle having a circularport 2 mm. in diameter, with the end of the nozzle located about 25 mm.to the point of impact.

The bundle was deflected upon an apron inclined at an angle of 35 andlocated 800 mm. from the point of impact. After being calendered at anip pressure of 30 kg./cm. and a temperature of 170 C., a fabric havinga weight of 150 grams per square meter, and a width of 800 mm., wasobtained, which was more homogeneous and wider than a spun-bondednon-woven fabric obtained in the identical process but without the useof the defleeting fluid jet (without the deflecting fluid jet, thefabric width was only 400 mm.).

Repeating this example, but using the deflector arrangement of FIGS. 8and 9 of the aforesaid U.S. Pat. No. 2,736,676 (that is, using a singleair jet located directly behind the point of impact, in relation to thedirection of the deflected filaments) resulted in the production of amore irregular spun-bonded fabric having a width of only 400 mm. In thisair jet arrangement, the air jet had no influence on the filamentbehavior other than accelerating the filaments leaving the deflectorsurface, to enable the deflector filaments to be thrown a greaterdistance from the point of impingement (Which is consistent with theteaching of the aforesaid U.S. patent).

What is claimed is:

1. In a process for manufacturing spun-bonded nonwoven textile fabrics,said process comprising extruding a plurality of filaments of afiber-forming polymer, orient ing the extruded filaments by stretching,and distributing the filaments on a receiving surface by impinging thefilaments upon a smooth deflector surface, the improvement comprisingspreading the filaments without destroying the filament bundle symmetrydirecting a fluid jet to the point of impact of said filaments on saiddeflector surface, said fluid jet being at an angle of 30-135 to theaxis of the filaments prior to said point of impact and located in frontof the point of impact in relation to the direction of the deflectedfilaments and in substantially the same plane 8 as the axis of theimpinging filaments and the average axis of the deflected filaments.

2. The process according to claim 1, wherein said fluid jet is a gasjet.

3. The process according to claim 2, wherein said gas jet is dischargedthrough a nozzle having a diameter or minimum width of 0.5 mm. and amaximum diameter or width of 5 mm., and wherein said gas is under apressure, prior to passing through said nozzle, of about 1-4 bars.

4. Process according to claim 3, wherein said gas is compressed air.

5. The process according to claim 1, including the additional step ofcalendaring the spun-bonded nonwoven fabric to improve the cohesivenessof said fabric.

6. The process according to claim 1 wherein said deflector surface is afiat surface.

7. The process according to claim 1 wherein said deflector surface is acurved surface.

8. The process according to claim 7 wherein said curved surface is asurface of revolution.

9. The process according to claim *1 wherein the major axis of saiddeflector surface is at an angle of 10 to to the axis of said filamentsprior to contact with said deflector surface.

10. The process according to claim 1 wherein said filaments arepneumatically stretched.

11. The process according to claim 10, wherein said filaments arestretched 200 to 400% of their original length.

12. The process according to claim 1, wherein said filaments arepolyester filaments.

13. The process according to claim 12 wherein said polyester filamentsare polyalkylene terephthalate filaments.

14. The process according to claim 1, wherein said filaments aretravelling at a speed of about 50 to about meters per second at the timeof impinging said defector surface.

References Cited UNITED STATES PATENTS 3,692,618 9/1972 Dorschner et all56l8l 2,736,676 2/19'5'6 Frickert, Jr. 156-16-7 3,314,840 4/1967 Lloydet al. 156-167 2,875,503 3/1959 Frickert, Jr. 156-467 DANIEL J. FRITSCH,Primary Examiner U.S. Cl. X.R.

